Implant and guide

ABSTRACT

A method for configuring a surgical guide and an associated implant. The implant and surgical guide are for maxillofacial osteosynthesis. Three-dimensional models of the pre- and post-operative anatomy are used to define attachment points. These attachment points are used to determine a structure for the implant and surgical guide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/090,466, filed Nov. 5, 2020, which is a continuation of U.S.application Ser. No. 15/096,645, filed on Apr. 12, 2016, which is acontinuation of U.S. application Ser. No. 14/737,340, filed on Jun. 11,2015, which is a continuation under 35 U.S.C. § 120 of InternationalApplication Number PCT/EP2013/076447, filed Dec. 12, 2013 (and publishedon Jun. 19, 2014 in the English language as WO2014/090964), which claimspriority to French patent application number 12/03393, filed Dec. 12,2012. Each of the above-referenced patent applications is herebyincorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a technique for repositioning boneportions for bone surgery, in particular for facial surgery, thetechnique being based on the use of customized implants and guides.

Description of the Related Technology

Some surgical interventions are intended to correct bone deformations,occurrences of disharmony or proportional defects of the face, orpost-traumatic after-effects. These interventions use actions forrepositioning, in an ideal location, some fragments of bone which havebeen separated from a base portion beforehand by a surgeon.

Such surgical interventions therefore comprise an osteotomy which iscarried out in order to release one or more badly-positioned bonesegments; for example, to move this or these bone segment(s), that is tosay, to move it/them by way of translation and/or by rotation in orderto be able to reposition it/them at their ideal location after thismovement.

When all bone segments occupy a new ideal position, the surgeon fixesthe bone segments to other adjacent bone portions of the patient usingfor one or more implants. These may comprise perforated implants, whichmay have different geometries, for example, in the form of I-shaped,L-shaped, T-shaped, X-shaped, H-shaped or Z-shaped plates, or morecomplex geometries. The implants are fixed to all the portions of boneto be joined in their correct relative positions using osteosynthesisscrews which extend through their perforations.

It is then, in this way, possible to seek to restore the symmetry of theface or normal anthropometric relationships.

U.S. Pat. Nos. 5,690,631 and 6,221,075 describe such implants in theform of plates or trellises which are capable of allowing at least twobone portions to be joined and fixed to each other.

Amongst the various forms of surgery which affect the facial skeleton,it is possible to mention:

-   -   orthognathic surgery, the objective of which is to reposition        dental bridges in relative comfortable positions, ensuring good        engagement of the teeth; such an intervention involves a        maxillary osteotomy if it is necessary to move the upper dental        bridge, or a mandibular osteotomy if it is necessary to move the        lower dental bridge, or a bi-maxillary osteotomy if it is        advantageous to move segments of bone on the two jaws in order        to also re-establish the normal proportions of a face,    -   genioplasty involving an operation on the chin of a patient for        aesthetic matters (in order to correct an excessively protruding        chin or in contrast a receding chin) or for functional matters,        for example, allowing a patient to be able to move his lips into        contact with each other without effort,    -   the correction of post-traumatic after-effects, for example,        with regard to the zygomatic bone, following accidental impacts.

A technique for producing a made-to-measure preformed implant isdescribed in an International Patent Application published on Nov. 3,2011 under the number WO 2011/136898. The technique therein comprisesthe production of a made-to-measure guide which is also pre-shaped andwhich serves to guide the drilling of some holes for the osteosynthesisscrews and which also serves to guide an osteotomy.

A disadvantage of the aforementioned prior technique is that it isdependent on the quality of the osteotomy, or the resection operation,carried out by the surgeon.

An object of certain embodiments of the invention disclosed herein is toovercome such a disadvantage. For example, it is desired to haveexcellent connection of the first portion of the bone and the secondportion of the bone, even if the osteotomy and/or the resection were tobe imperfect, imprecise and even approximate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 9 illustrate a method according to an example that allows adevelopment of a made-to-measure implant and drilling guide.

FIG. 10 a illustrates a longitudinal section of a drill bush associatedwith a drilling guiding hole of an example drilling guide, the drillbush being associated with a stop bit.

FIG. 10 b shows an osteotomy fixing device in situ within a drilledbore.

FIGS. 11 to 19 illustrate different steps of an orthognathic surgicaloperation that can be carried out using the drilling guide and theimplant obtained by carrying out the method illustrated in FIGS. 1 to 9.

FIGS. 20 to 25 illustrate a second example method applied to chinsurgery.

FIGS. 26 to 31 illustrate a third example method applied to thereconstruction of a mandible.

FIGS. 32 and 33 illustrate a fourth example with multiple guides andimplants.

FIGS. 34 a and 34 b illustrate a variation of the examples.

FIGS. 35 a and 35 b illustrate the avoidance of high-risk anatomicalareas.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

Techniques used in certain examples described herein involve producing apre-operative model and a modified model of a complete bone in threedimensions. In certain cases these models are digitalized and used toproduce an implant and/or drilling guide. The implant and/or drillingguide may be bespoke, i.e. made-to-measure or customized for a patient.

In cases, pre-operative planning of the repositioning operations to becarried out for various bone fragments or portions is desirable in orderto define an ideal position of the bone fragments or portions.

The pre-operative planning generally uses radiography studies ortomodensimetric scanner sections. These imaging data are then processedon a computer using a specific application to generate athree-dimensional reconstruction of the images. For example, this stagemay comprise accessing data indicative of a pre-operative maxillofacialanatomy of a patient and generating a three-dimensional model of saidanatomy using said data.

When the planning is complete, a pre-operative model of a bonestructure, such as a skull or a portion thereof, in three dimensions isproduced. This constitutes the pre-operative shape of the bone. Thisshape is then modified to produce a modified model corresponding to theplanned post-operative shape of the bone, in three dimensions.

Amongst the means to achieve this, a surgeon can, optionally incollaboration with an engineer, use a system of surgical navigation bymeans of which it will be possible for him to define on the modifiedmodel the various planes of section which will then allow the bonefragments to be moved, separated virtually from their base owing to theosteotomy, in order to move them in one or more directions to bedetermined in order to be able to reposition them in the correctlocation.

In this manner, an osteotomy is simulated on the three-dimensional modelof the pre-operative maxillofacial anatomy. In one case, said simulatedosteotomy defines at least one cut that results in one or more boneportions that are separated from other one or more bone portions. Incertain cases, said at least one cut results in an absence of any bonecoupling the bone portions together, i.e. the cut is a complete cut thatcompletely separates at least one bone portion from one or more otherbone portions. The cut may thus result in an absence of a continuousbone coupling between bone portions.

After this virtual osteotomy, the second step involves carrying out,still in a virtual manner, the ideal repositioning of various bonesegments.

The repositioning or arranging of one or more bone portions in relationto one or more other bone portions enables a modified three-dimensionalmodel to be generated. This model is indicative of a desiredpost-operative orientation of the bone portions.

To this end, the surgeon generally uses criteria of symmetry orcephalometry.

The repositioning operations carried out are transformations whichcombine movements in translation and/or in rotation. In one case, thearrangement may comprise at least one or more of a translation of theone or more bone portion in relation to one or more other bone portionsand a rotation of the one or more bone portions about an axis that isorientated at a non-zero angle to an osteotomy plane, e.g. at least oneplane of a virtual osteotomy cut within an original pre-operative model.In more complex operations the osteotomy may be according to a complexshape that resides in multiple planes. In certain cases, in the surgicalprocedure that follows the virtual osteotomy, the cut may be partial,with a complete separation being achieved by one or more fracturesapplied by a surgeon.

It is during this second step that the surgeon also defines any bonezones to be resected in the event that some bone fragments could overlapeach other when they are moved together, at least as the surgeon seesthem on the computer screen.

A technician or an engineer, possibly in close collaboration with thesurgeon, may thus physically design during a third step one or moreimplants. In one case, they may also be responsible for the virtualosteotomy and/or repositioning, and/or this may be performed inassociation with a medically trained professional. Following themanufacture of the one or more implants according to the design, asurgeon is able to fix said implants to the different bone fragments,after having carried out an actual, as opposed to virtual, osteotomyoperation. The operation may also optionally include a resectionoperation. The operation maintains the bone fragments in the correctposition, which are secured by way of the one or more implants. Theimplants may remain for the time necessary for good reconstruction andgood bone consolidation.

Certain examples are set out in the following description together withthe appended drawings. It should be noted that these drawings areintended only to illustrate the text of the description and as such arenot limiting.

In certain examples, there is a method which involves producing in amade-to-measure state one or more of (a) a pre-shaped implant and (b) apre-shaped guide which is used to guide the drilling of holes for allthe screws required for the future fixing of the implant to the portionsof bone to be fixedly joined together after a maxillofacial osteotomyoperation. The pre-shaped guide may also, in certain cases, comprise anosteotomy template to guide the osteotomy. One example method will bedescribed with reference to FIGS. 1 to 9 .

The orthognathic surgery, the different preparation phases of which areillustrated by way of first example in FIGS. 1 to 9 , is intended torepair an occurrence of asymmetry, the intervention involving in thisinstance a maxillar osteotomy. In certain case, this could be combinedwith chin surgery of the type illustrated in FIGS. 20 to 25 .

As described above, a technician, most often in collaboration with asurgeon, using a computer, first produces a pre-operative model 40 ofthe bone, in three dimensions, which constitutes the pre-operative shapeof the bone (FIG. 1 ). For example, in this case the pre-operative modelis of a portion of a skull. The model of the bone may be a model of acomplete portion of bone involved in a repositioning operation.

Using dedicated planning software, for example, the software marketed bythe Belgian company Materialise under the name Mimics, a user, typicallya medically trained professional such as a surgeon, optionally assistedby a technician, modifies the pre-operative model by carrying out avirtual osteotomy 3 (FIG. 2 ), following which he arrives at a modifiedmodel 50 which gives the ideal result which is desired by the surgicalintervention and consequently corresponds to a planned shape of the bone(FIG. 3 ). For example, this may be a desired post-operative orientationof the first and second bone portions. The model is modified at apre-operative stage. In FIG. 3 the ideal result is an arrangement of anupper jaw portion (2) with respect to the skull (1). This for examplemay reflect a desired alignment of the upper and lower jaws, analignment via trauma or fracture of the bone, and/or an alignment tocorrect a deformity.

As has been said above, at the same time as he virtually carries out hisosteotomy, the user, such as a surgeon, may envisage carrying out one ormore resection operations in the event of interference between some bonefragments, in order to achieve perfect positioning of the separatedportion of the bone 2 in the portion 1 of the base bone.

In the present description, the portion 1 of the base bone will bereferred to as “first portion of the bone” and the separated portion 2(or the separated portions) will be referred to as “second portion ofthe bone”. However, as described elsewhere in this specification, themethod may apply to multiple bone portions, such that one or more of thefirst and second bone portions may comprise a plurality of bonefragments, and/or relate to other bone portions to be repositioned.

After ideal repositioning of the second portion 2 of the bone on thefirst portion 1 in the virtual three-dimensional space of the modifiedmodel, the user defines the future fixing locations for the two portionsof bone using one or more implants. In this case the fixing locationsare associated with the axes of the osteosynthesis screws which ensureperfect fixing of the one or more implants on the portions of bone to befixedly retained in their desired correct relative position by the user.

Such fixing locations 4 (for example, eight in number in the firstportion 1 of the bone and also eight in the second portion 2 of thebone) are provided in sufficient numbers to ensure anchoring of thesecond portion 2 of the bone on the first portion 1 (FIG. 4 ).

In the present examples, the future fixing locations, referred to hereas attachment points, comprise a first plurality of attachment pointsfor the implant on the first bone portion and a second plurality ofattachment points for the implant on the second bone portion. Forexample, in FIG. 4 there are eight points on each bone portion.

As described above and shown in FIG. 4 , the first and second pluralityof attachment points are defined on the modified three-dimensional modelbased on at least one location of one or more anatomical features of apatient. For example, fixing locations or attachment points may bedefined to avoid numerous anatomical obstacles such as at least one ormore of the following: teeth roots, nerves and/or blood vessels insidethe bone portions. Likewise, some bone parts are very thin, e.g. this isespecially true of maxillary regions, which leading to difficulties toobtain stable osteosynthesis. By defining the fixing locations, screwscan be individually placed in the most favorable locations to ensuresuccessful repositioning without complication; for example, with greatlyreduced risk of damaging any important anatomical structure and withscrew placement in regions with the best bone quality.

In practice, as shown in FIG. 4 , this results in, when compared with acomparative example, at least a spacing distance between a first set ofadjacent attachment points being different from a spacing distancebetween a second set of adjacent attachment points. In this case thefirst and second sets of adjacent attachment points comprise either: twosets of attachment points with each set comprising adjacent attachmentpoints on the same bone portion; or two sets of attachment points witheach set comprising a first attachment point on the first bone portionand a second, adjacent attachment point on the second bone portion. Thismeans that the attachment points are typically not defined in a standardsquare or rectangular relationship: individual placement leads tovariation in the relative spacing between attachment points. Not allfixing locations need to be individually placed, but at least one isplaced so as to avoid high-risk areas of anatomy.

According to certain examples described herein, following the definingof the fixing locations or attachment points, a monolithicthree-dimensional structure is defined for the implant. This structurecouples the first and second plurality of attachment points in themodified three-dimensional model. The defined structure has a shape thatvaries in each of three dimensions to arrange or align the second boneportion relative to the first bone portion in accordance with thedesired post-operative orientation. In this case, each of at least oneof the attachment points correspond to an aperture for a bone fixationdevice in said structure for the implant, e.g. each fixing location maycorrespond to a hole where a bone screw fixes the implant to a boneportion.

For example, the user may subsequently draw the implant 5 which can beseen in FIG. 9 . The sixteen osteosynthesis screws which ensure that theimplant is fixed in the first and second portions of the bone aredesignated by the locations 6. These screws correspond precisely to thefixing locations or attachment points 4, which can be seen in FIG. 4 .

In the above example, the fixing locations or attachment points aredefined prior to the structure of the implant; in effect, the structureof the implant is designed around the placement of the fixing locations.For example, in FIG. 9 , the implant comprises portions in the form ofmembers that couple certain adjacent apertures for the attachmentscrews.

The implant 5 is thus arranged at a pre-operative stage so as tocorrespond to the planned post-operative shape of the desired anatomy.As well as being customized in the form of customized couplings betweenindividually placed screw apertures, the implant 5 is also pre-shaped insuch a manner that the congruence of surfaces of intrados thereof allowsunique and precise positioning on the two portions of bone to be joinedat the end of the surgical operation. In other words the implant has ashape that varies in three dimensions to arrange the second bone portionrelative to the first bone portion in accordance with the desiredpost-operative orientation and the implant has a shape that matches theanatomy of both the first and second bone portions. The term intrados,meaning the underside of an arch, is used to refer to the curvature ofthe implant, in particular in the present example, an inner curvaturethat mates with an outer curvature of the bone portions. Such curvatureis bespoke for each patient, the example the inner surface of theimplant 5 may vary in a non-uniform manner with multiple undulationsthat reflect the anatomy of the patient. In this case, a first portionof the implant structure has a three dimensional shape, including adefined inner surface or plane, that matches an outer surface or planeas defined by the anatomy of the first portion of bone, i.e. the upperskull. A second portion of the implant structure then has a threedimensional shape, including a defined inner surface or plane, thatmatches an outer surface or plane as defined by the anatomy of thesecond portion of bone, i.e. the upper jaw portion that is to berealigned with respect to the upper skull.

The implant 5 extends at both sides of one or more osteotomy lines 7.The one or more osteotomy lines 7 each define a cut containing the linewhich separates the two portions of bone 1, 2. The structure of theimplant 5 comprises, with respect to the second portion 2 of the bone,through-holes for screws that correspond to drilling guiding holes orattachment points for screws as defined on the modified model.

The implant 5 may be manufactured or produced based on the definedstructure, e.g. based on a three-dimensional model such as that shown inFIG. 9 . The implant may be manufactured by additive manufacturing, forexample it may be printed in three dimensions or selective lasersintering.

In contrast to comparative examples, the through-holes of the implant 5,for the passage of the screws which are intended to allow the implant tobe fixed to the first portion of the bone, are not provided in acompletely arbitrary, unplanned manner. Instead in certain examplesdescribed herein, such holes, with respect to the first portion 1 of thebone, are provided so as to correspond to the attachment points orfixing locations as defined on the modified model.

In the presently described example, using a computer application, auser, e.g. a technician in certain cases assisted by a surgeon, carriesout a reverse transformation of the ideal repositioning which he hascarried out. In other words he returns to the pre-operative model of thebone which constitutes the pre-operative shape of the bone. In this casethe first and second plurality of attachment points are mapped tocorresponding locations on the three-dimensional model of thepre-operative maxillofacial anatomy.

For example, on the original model of the pre-operative maxillofacialanatomy (FIG. 5 ), the user defines, for example, using virtual modelsof drill bushes or bits 8, the positions of the bores. In this casethese positions are derived from, i.e. correspond to, the fixinglocations 4 planned previously with respect to the modified model (FIG.4 ). In the example shown in FIGS. 1 to 9 , the fixing locations 4 onthe first portion 1 may be mapped directly between the modified andunmodified models: the location of the first portion of bone 1 in threedimensional space does not change between the modified and unmodifiedmodels. In the same example the fixing locations 4 on the second portion2 are mapped based on their relative positioning with respect to thesecond portion 2. In this latter case, the location, position and/ororientation of the second portion changes with respect to the firstportion between the modified and unmodified models as a result of thevirtual osteotomy. Hence, the fixing locations 4 may be mapped byapplying a function that is inverse to a function defining thetranslation and/or rotation that resulted from the virtual osteotomy. Inboth cases the mapping may be achieved by applying a function to a threedimensional co-ordinate or model component.

Following the mapping stage, a monolithic three-dimensional structurefor the surgical guide is determined that couples the correspondinglocations in the three-dimensional model of the pre-operativemaxillofacial anatomy. For example, in one case a user may “draw” orotherwise define within the virtual model, the surgical guide whichcorresponds to the pre-operative shape of the bone and which comprisesthe drilling guiding holes for the fixing screws. In a preferred case,the position of the osteotomy or the osteotomies to be carried out mayalso be defined by way of the surgical guide structure. An exemplarysurgical guide as defined as a three-dimensional model is shown in FIG.6 .

The drilling guide 9 which is defined in this manner and which can beseen in FIG. 6 consequently comprises:

-   -   drilling guiding holes for the screws corresponding, in terms of        the second portion 2 of the bone which must be separated, to the        drilling guiding holes for the screws of the modified model        provided with respect to the second portion,    -   two notches 10 and 11 which correspond to the templates of the        future osteotomies.

The notches may comprise elongate openings with the three dimensionalguide structure that are arranged to allow a passage of a cutting tool,such as a bone saw, to perform the respective one or more osteotomies.

As was the case for the implant, the drilling guide is configured sothat there is excellent correspondence between the surfaces of theintrados thereof and the bone support or anatomy of the patient. In thismanner there exists only one possible position for such a guide withrespect to the anatomy of the patient; e.g. the guide may only sit flushwith the bone portions of the patient in one unique spatial position orconfiguration. In this case, if the guide is placed in an incorrectorientation with respect to the bone portions the guide, it will not sitproperly, i.e. it will be in an unstable configuration, such thatmovements to work the guide into a correct configuration result in astable mating of an inner surface defined by the guide and an outersurface defined by the bone portions. This enables a simpler and moreprecise surgical operation to be carried out at a later stage.

The guide 9 according to the present example comprises drilling guidingholes for the screws for the first portion of the bone (in additional tothose for the second portion of bone), the precise position of theseholes having been defined during the operation which can be seen in FIG.4 .

FIG. 7 shows the pre-operative or unmodified model in which a pluralityof bores have been defined in the first and second bone portions withinthe model for the passage of the screws which are intended to allow thefuture fixing of the implant 5. In this case the relative spatialarrangement of the bores is different from the relative spatialarrangement of the fixing locations 4 seen in FIG. 4 because, at thestage illustrated in FIG. 7 , the virtual osteotomy and repositioningoperations have not yet been carried out. These bores represent theholes that are to be drilled for previously-defined fixing locations orattachment points.

FIG. 8 shows the different locations of a plurality of drill bits 8 (orat least an end portion of a drill bit) in the first portion 1 of thebone and second portion 2 of the bone after osteotomy, but beforerepositioning. In this case the drill bits 8 are modelled within thevirtual three-dimensional model. Further detail is shown in FIGS. 10 aand 10 b . Modelling the drill bits 8 may aid in defining the height ofone or more drill bushes 15 as described later below.

Finally, FIG. 9 shows a simulation of the two portions of the bonejoined after an osteotomy and repositioning operations. Once the implant5 and guide 9 have been determined, i.e. designed, within a virtualthree-dimensional space they may be manufactured for use in theosteotomy and repositioning operations. FIG. 9 is thus illustrative ofthe use of an implant 5 following surgical operations. The joining ofthe two portions of bone is securely held using the implant 5. Theimplant may remain indefinitely or as long as a medical professionaldeems it necessary to allow the two portions of bone to be fixed andconsolidated. For example, in a case similar to FIG. 9 bone may grow tojoin both the first and second portions in the configuration set by theimplant 5.

FIGS. 1 to 9 illustrate the different preparation phases in thecustomized production of a pre-shaped implant 5 and a pre-shaped guide9. Following this, the orthognathic surgical operation in which amanufactured implant and guide may be used will now be described withreference to FIGS. 11 to 19 .

The facial skeleton 40 to be repaired is illustrated in FIG. 11 whichmirrors the virtual model of FIG. 1 .

A surgeon places the guide 9 which is produced in a made-to-measurestate on the face of the patient. In one case, e.g. if the operation isto be simple and brief, the guide 9 may be held by hand in the positionshown in FIG. 12 . In another case, e.g. if the operation is to berelatively long, the guide may be temporarily fixed using one or moreosteotomy screws, for example on one or more sides of the osteotomy orcutting template 3, as shown in FIG. 13 . In certain cases at least oneof said one or more apertures for attaching the surgical guide 9 isco-incident with a defined osteotomy cut.

In both the above cases, i.e. in relation to FIG. 12 or FIG. 13 , thedrilling guide 9 is held in a stable state. In this case, the surgeonthen drills the bores (sixteen in number in this example) at theprovided locations corresponding to the drilling guiding holes in theguide. For example, FIG. 14 shows at least a portion of a drill bit 8being inserted into one of the guiding holes of the guide 9 so as todrill a bore.

If the guide 9 has been stabilized by one or more osteotomy screws, thebores generated by these screws may take the place, in an equivalentnumber, of a respective one or more bores to be provided at theappointed locations, i.e. at the fixing locations or attachment points.

In certain cases, as part of the stage of defining fixing locations anangle of orientation for an axis associated with one or more of thebores may be also defined based on at least one location of one or moreanatomical features of the patient. This axis may be offset from thenormal, i.e. offset from an axis perpendicular to the surface of thebone portion.

The surgeon can then, in accordance with his preferences, either drawusing a pencil or a surgical felt-tip pen the osteotomies delimited bythe notches 10 and 11, or immediately use these notches to initiate theosteotomies. This is shown in FIG. 15 .

The surgeon then removes the guide, after having removed the temporarystabilization screws, if he had placed any of them. In one case, using atool 20, for example, a saw, a milling cutter, a laser, etcetera, hefinalizes or carries out the osteotomy operation 12, 13 which allows himto release, and therefore move, the maxillary. This is shown in FIG. 16.

The surgeon can consequently in future freely move the second portion 2of the bone and bring it into contact with the first portion 1 of thebone, in their desired relative position as is shown in FIG. 17 . Due tothe customized nature of the structure of the implant 5, the surgeon isonly able to fix the two portions 1 and 2 in a single desired positionor configuration using the implant 5. For example, it is only in oneposition or configuration in three-dimensional space that the axes ofthe apertures for the osteosynthesis screws 6 provided for constructionin the implant 5 will correspond to the bores produced in the two boneportions during the operation seen in FIG. 14 . This is shown in FIG. 18.

Finally, it is sufficient for the surgeon to definitively fix the twobone portions 1 and 2 using the implant 5 by inserting osteosynthesisscrews 6 at their fixing locations 4 and thus screwing them into thesixteen bores produced in the bone portions. This is shown in FIG. 19 .

It was set out previously that the precise positions of the bores whichare intended to receive the future screws of the implant 5 wereindicated on the modified model. Therefore, in one case, the positionsof all the bores is produced in a planned manner before the osteotomy iscarried out. This in turn means that in surgery the bores and fixinglocations are fully defined by the guide 9 and implant 5. This reducesthe need for precision during the later surgical operations.

In one particular example, in accordance with a knowledge of the anatomyof the patient, it can be ensured that the bores for the osteotomyscrews do not contact any deep-lying major organ. For example, thesurgical guide 9 may be defined such that the bores are subsequentlyguided during drilling to avoid certain anatomical areas.

To this end, as shown in FIGS. 10 a and 10 b , one or more drill bushes15 are defined that are either insertable into each of the drillingguiding holes of the guide or form part of guide structure defining theholes. According to this particular example, a drill bush 15 has aheight which is predetermined to avoid high-risk anatomical features ofthe patient. Additionally, or alternatively, a drill bush 15 may beconfigured such that a subsequently drilled bore 14 has an axis oforientation that also avoids high-risk anatomical features of thepatient.

FIG. 10 a shows a drill bit 8 that is used to drill a bore 14. The bore14 then receives an osteotomy screw 6 to fasten the implant 5 and/orguide 9 to the bone portions of the patient as shown in FIG. 10 b . InFIG. 10 a , the drill bush 15 comprises a stop 16. In use the stop 16halts the penetration of the drill bit 8 into the bone portions. In moredetail, in one example, the stop 16 is formed from a cylindrical upperportion of the drill bush 15, wherein the edge of the upper portioncomprises a ledge that extends substantially perpendicular to an axisfor the bore 14 and the drill bush 15. This ledge (which in certainexamples may comprise a rim, collar or flange) comes into contact with acorresponding collar of the drill bit 8 to prevent further movement ofthe drill bit 8 along the axis for the bore and the drill bush 15.

In this manner, in addition to or instead of, the precise position ofthe bores 14, certain exemplary methods ensure that the axis and thedepth of the bores is precisely guided. For example, as seen in FIG. 6the drill bush 15 may form a customized portion of the guide structure,wherein each guiding aperture may comprise a drill bush with acustomized height. These drill bushes then form part of the completemanufactured guide structure.

The osteotomy screws 6, one of which is illustrated in FIG. 10 b , aretherefore at no risk of touching a nerve, a dental root or a vein (i.e.high risk areas of anatomy) when they are screwed into the bonefragments of the patient.

As described herein, the relative spatial arrangement of a plurality ofholes for the passage of screws used to secure an implant correspond tothe relative spatial arrangement of a plurality of drilling guidinglocations. It is possible to configure multiple applications of thedescribed method in the field of facial surgery, for example, in orderto repair faults of the mandible, the chin or at least one of the twozygomatic bones.

In this manner, FIGS. 20 to 25 show an application of the method to chinsurgery in a second example.

FIG. 20 shows the chin 21 to be repaired.

FIG. 21 schematically illustrates along line 22 the osteotomy definedvirtually. It further schematically illustrates along line 23 areference point of a resection which is also desired and definedvirtually.

FIG. 22 shows the chin as it should be after the double operation ofosteotomy and resection, followed by the repositioning of the secondportion 24 of the bone relative to the first portion 25.

It is known that, on the basis of the final result illustrated in FIG.25 , the following are defined in advance:

-   -   a) the position of the fixing locations 26 of the implant which        will fixedly join the portions of bone 24 and 25 in their ideal        relative position,    -   b) the implant 27, and    -   c) the drilling guide 28.

FIG. 23 shows a virtual model of the chin 23 to be repaired. In relationto the chin depicted in the model, in use at a later point, a surgeonmay press the drilling guide 28 which is produced in a made-to-measurestate. The model of FIG. 23 also shows the result of a resection. InFIG. 23 four drilling guiding holes have been provided in the guide 28.In use, the drilling guide holes guide one or more drill bits to form aplurality of fixing locations 26 which will receive the four fixingscrews of the implant 27.

An illustration of four holes 26 drilled in this manner can be seen inFIG. 24 which simultaneously shows the chin as it must be in the idealfinal position thereof, that is to say, after the guide 28 has beenwithdrawn, after osteotomy, after resection and after repositioning ofthe two bone pieces 24 and 25.

Finally, FIG. 25 illustrates the fixing of the two bone portions of thechin repaired in this manner using the implant 27 which is provided withthe four osteosynthesis screws thereof.

By way of a third variant, FIGS. 26 to 31 show an application of thedescribed methods to a mandible reconstruction.

FIG. 26 shows the mandible 40 to be repaired. FIG. 27 shows the cut 29of the osteotomy defined virtually and FIG. 28 shows, still in a virtualmanner, the ideal relative repositioning desired for the two boneportions 30 and 31 which were separated as a result of the virtualosteotomy.

FIG. 28 therefore shows the post-operative shape 50 of the completebone.

Based on this modified model, therefore, the position of the fixinglocations 32 of the future implant 33 are precisely defined as describedabove. This is shown in FIG. 29 . Consequently, by the reversetransformation applied by the computer application and returning to thepre-operative model, the position of the drilling guiding holes of thefuture drilling guide 34 are defined.

It is seen in FIG. 29 that, in this example, the implant 33 issubstantially in the form of an I-shaped plate. There are three fixinglocations 32 for osteosynthesis screws, which are aligned with respectto the first portion of the bone 30, and three fixing locations 32,which are aligned with respect to the second portion of the bone 31. Inthis example, the six fixing locations 32 are themselves arrangedsubstantially in the same alignment.

Having defined the position of the fixing locations or attachmentpoints, and the implant 33 having been drawn, the pre-operative model ofFIG. 26 is returned to the drilling guide 34 is determined in such amanner that it will comprise:

-   -   six drilling guiding holes 35 which are provided so as to        correspond to the six fixing locations 32 after the two bone        portions 30 and 31 have been returned to the positions which        they occupied before the osteotomy,    -   a notch 36 which is cut in the central portion of the guide 34        in order to act as a reference point, either for drawing the        osteotomy line or for initiating the osteotomy.

It is thus simply necessary for the surgeon to place the guide 34 on themandible of the patient as demonstrated in FIG. 3 ), to drill in thebone portions 30 and 31 the six fixing locations 32 using for thispurpose the six drilling guiding holes 35 of the guide 34, to remove itand to carry out completely or, at the very least, to end the osteotomyoperation, following which the mandible of the patient will correspondto that illustrated in FIG. 27 , supplemented by six locations 32 whichare intended to receive the six fixing screws at the end of theintervention.

After repositioning the two bone portions in the ideal relative locationdesired at the outset, a location which is illustrated in FIG. 29 , asurgeon then has only to position the implant 33, screwing the sixosteosynthesis screws 6 into the six pre-shaped holes 35. FIG. 31 isthus representative of the state of the completed surgical operation.

In one case, for the applications of the method described above by wayof examples, each implant and/or each drilling guide is produced fromtitanium.

FIG. 32 shows an example wherein the above-described methods arerepeated to determine a plurality of monolithic three-dimensionalstructures for a plurality of surgical guides 44. In the case of FIG. 32the methods are repeated for a plurality of first bone portions 1 and acommon second bone portion 2. In FIG. 33 the above-described methods arerepeated to determine a plurality of monolithic three-dimensionalstructures for a plurality of implants 45. As can be seen, in thisexample, one structure for a surgical guide corresponds to a pluralityof structures for an implant. Such an adaptation may be applied theother way round in other examples, e.g. a plurality of structures for asurgical guide may correspond to one structure for an implant. In FIGS.32 and 33 the second bone portion 2 is a portion of zygomatic (i.e.cheek) bone; the maxilla may be seen to the right of the Figures withthe eye socket in the top left quadrant of the Figures and the nasalcavity towards the top of each Figure.

FIGS. 34 a and 34 b demonstrate how a portion of a first structure for afirst implant or first surgical guide may be defined and subsequentlymanufactured that distinguishes said first structure from a secondstructure for a second implant or second surgical guide. For example,protrusion 47 a in FIG. 34 a distinguishes the upper implant, for use onone side of a jaw, from another similar lower implant with a differentprotrusion 47 b shown in FIG. 34 b for use on the other side of the jaw.

FIGS. 35 a and 35 b show a nerve 51 and a tooth root 53. It can be seenin FIG. 35 a how a proposed bore for a screw 6 is defined to avoid thenerve 51 by distance 52. This may be achieved by defining one or more ofthe depth and orientation of the bore, which is then used to define theguide structure. Likewise said bores in FIG. 35 b , in use filled withthe screws 6 of the implant, also avoid the tooth root 53.

In a comparative example, the osteotomy, and/or the resection operation,must be strictly in accordance with that/those which the surgeon haspreviewed virtually on his computer. This is because, when the surgeonfixes an implant to a portion of the bone which has been separated, hewill need to fix the implant to a first portion of the bone using a fewscrew passage holes which have been provided in a completely arbitrary,non-programmed manner. For example, they may be based on fixing holeswhich have been pre-drilled in an arbitrary manner. On this occasion itis difficult to correct any imperfection of the osteotomy operationand/or the resection operation. However, according to methods describedherein the pre-determined attachment points and the associated bores asguided by the custom drill guide, ensure a precise alignment of boneportions and reduce the effect of any imperfections in the osteotomy.

In an example, there is a method for producing together, in amade-to-measure state, a pre-shaped implant arranged in order, usingscrews, to fix a first portion of a bone to a second portion of thisbone which must be separated from the first portion by an osteotomyoperation, and a guide which is also preformed for guiding the drillingof holes for the screws and for guiding the osteotomy. In such a method,there are the steps, before the osteotomy operation, of:

-   -   a) using a computer, producing a pre-operative model of the        complete bone, in three dimensions, constituting a pre-operative        shape of the complete bone, and modifying the pre-operative        model, in order to produce a model modified by the fact that it        comprises:        -   a1) a planned post-operative shape of the complete bone, and        -   a2) drilling guiding holes for the screws in the second            portion of the bone which must be separated and at least one            reference point for the osteotomy template,    -   b) then producing in a made-to-measure state:        -   b1) a pre-shaped bone fixing implant which is arranged in a            pre-operative manner so as to correspond to the planned            post-operative shape of the complete bone, the implant            comprising a pre-shaped element in order to allow the first            portion and the second portion of the bone to be fixed to            each other, by producing on the pre-shaped implant, for the            second portion of the bone which must be separated,            through-holes for the screws corresponding to the drilling            guiding holes for the screws of the modified model, by            providing in an arbitrary, non-planned manner in the            pre-shaped implant holes for the passage of screws which are            intended to allow the implant to be fixed to the first            portion of the bone, and        -   b2) a pre-shaped drilling guide which is arranged in a            pre-operative manner so as to correspond to the            pre-operative shape of the complete bone, by producing on            this guide, for the second portion of the bone which must be            separated, drilling guiding holes for the screws            corresponding to the drilling guiding holes for the screws            of the modified model.

During the operation for modifying the model seen in step a), there mayfurther comprise:

producing on the modified model, in addition to the drilling guidingholes for the screws provided for the second portion of the bone whichmust be separated and the osteotomy template reference point(s),additional drilling guiding holes for the screws for the first portionof the bone,

-   -   2) during the operation for made-to-measure production seen in        step b), producing on the pre-shaped drilling guide additional        drilling guiding holes for the screws for the first portion of        the bone and ensuring that the holes provided in the implant for        the passage of the screws which are intended to allow the        implant to be fixed to the first portion of the bone correspond        to the additional drilling guiding holes produced in the        modified model, the complete relative spatial arrangement of all        the passage locations for the screws produced using the drilling        guide on the modified model corresponding to the complete        relative spatial arrangement of all the holes for the passage of        the screws produced on the implant.

In certain examples described herein, specific features of at least oneguide and at least one implant are determined and/or produced in amade-to-measure state. In this case a guide is, to some degree,configured to correspond to the initial situation to be corrected and animplant is, to some degree, configured to correspond to the idealplanned situation. In this case, a correspondence is made between thedrilling guiding holes for the fixing screws for the first portion ofthe bone and the through-holes for the screws for the first portion ofthe bone produced in the implant. This results in the implant, owing toits construction, accurately joining the first portion of the bone withrespect to the second portion(s) of the bone, even if the osteotomy, orthe resection, is imperfect or approximate.

Consequently, by using a guide and/or implant as described herein asurgeon need not delay carrying out an osteotomy, and optionally aresection operation, due to the need to have the greatest precision. Heknows in advance that the implant will ideally join all the portions ofbone in the region of the face of the patient he is dealing with sincethe guiding holes of the fixing screws all have defined positions, bothon the first portion of the bone and on the second portion(s) of thebone.

In order to reduce the risk of touching a deep-lying major organ, forexample, a nerve, a vein, a dental root, etcetera, methods as describedherein make provision, in addition to the precise position of each borewhich is intended to receive a fixing screw, for the drilling axisand/or the depth thereof also to be determined in a precise manner.

In this manner, a drilling guide as described in examples hereincomprises, with respect to at least one of the drilling guiding holeswith which it is provided, a drill bush whose axis will correspond tothe drilling axis and whose height will be such that it will secure thedrilling by limiting the depth thereof in order to eliminate any risk ofbringing the drill bit into contact with a major organ.

Certain methods described herein make provision for the second portionof the bone which must be separated from the first portion by anosteotomy operation to be able to be separated itself into severalfractions.

Examples described herein also relate to a pre-shaped implant which isobtained by carrying out certain methods described above. This implantis intended to fix, using screws, a first portion of a bone to a secondportion of this bone which must be separated from the first portion byan osteotomy operation. The implant is produced in a made-to-measurestate so as to correspond to the modified model which constitutes theplanned post-operative shape of the complete bone. This implantcomprises, for the second portion of the bone which must be separated,through-holes for the screws which correspond to the drilling guidingholes for the screws of the modified model. The implant is determinedsuch that it further comprises, for the first portion of the bone, holesfor the passage of the screws, which holes correspond to the drillingguiding holes produced in the modified model for the screws which areintended for the first portion of the bone.

The implant described in the example above therefore has, with respectto the first portion of the bone, holes for the passage of fixing screwsthat are planned and correspond to the drilling guiding holes producedin the modified model for the screws which are intended for this samefirst portion of the bone.

In other words, the complete relative spatial arrangement of some or allof the holes for the passage of the fixing screws produced in theimplant corresponds to the complete relative spatial arrangement of someor all of the drilling guiding holes for the screws, produced in themodified model. The implant can therefore occupy only one position onthe face of the patient, after the osteotomy operation and after anyresection operation. It is therefore of no consequence that theosteotomy and/or the resection is/are imperfect or approximate.

An important factor is that, after fixing the implant using theosteosynthesis screws, the second portion of the bone or the secondportions of the bone is excellently positioned relative to the firstportion of the bone. Thus, after the bone reconstruction and the joiningof all of the operated zone, the first and second portions of the boneof the patient will be joined as originally desired.

In the same context, examples described herein relate to a pre-shapeddrilling guide which is obtained by carrying out the method describedabove and which is intended to guide the osteotomy and/or guide thedrilling of holes for the screws which are used to fix, using theimplant which has also been described above, a first portion of a boneto a second portion of this bone. The guide is produced in amade-to-measure state and comprising, for the second portion of the bonewhich must be separated, drilling guiding holes for the screwscorresponding to the drilling guiding holes for the screws of themodified model, the drilling guide being configured such that it furthercomprises, for the first portion of the bone, drilling guiding holes forthe screws, which holes correspond to the drilling guiding holesproduced in the modified model for the screws which are intended for thefirst portion of the bone.

In certain examples, in contrast to comparative drilling guides, adrilling guide extends from both sides of a line along which theosteotomy is due to be carried out. By projecting beyond this line,numerous holes may be provided for guiding the drilling of the screwswhich are intended to be fixed in the first portion of the bone.

Furthermore, the position of these holes is predetermined in terms ofproduction so as to correspond to the holes that are defined in themodified model with respect to the first portion of the bone.

A consequence of this construction is that, after all the planned holeshave been drilled, using the guide, in the first and second portions ofthe bone, after the osteotomy has been supplemented by the optionalresection, and finally after the planned repositioning of the boneportions, in accordance with what was envisaged at the outset, thecomplete relative spatial arrangement of some or all of the passagelocations for the screws produced using the drilling guide is such that,in the repositioned portions of the bone, it corresponds precisely tothe complete relative spatial arrangement of some or all the holes forthe passage of the screws produced in the implant.

That is to say, the drilling guide in with certain examples describedherein ensures that some or all of the holes drilled before theosteotomy in the first and second portions of the bone, after theosteotomy and the ideal repositioning of the portions of the bonecarried out by the surgeon, are in alignment with the holes which havebeen drilled in the pre-shaped implant.

Finally, examples relate to a kit or assembly which is constituted by animplant and a drilling guide which are produced together in amade-to-measure state. In this case the complete relative spatialarrangement of some or all of the passage locations for the screwsproduced using the drilling guide, on the modified model, correspond tothe complete relative spatial arrangement of some or all of the holesfor the passage of the screws produced in the implant. For example,locations of the first and second plurality of apertures in themaxillofacial surgical guide correspond to mapped locations of the firstand second plurality of apertures in the maxillofacial implant, whereinthe locations of the first and second plurality of apertures in themaxillofacial surgical guide correspond to a pre-operative maxillofacialanatomy, and wherein the locations of the first and second plurality ofapertures in the maxillofacial implant correspond to a desiredpost-operative maxillofacial anatomy.

The examples described above are not limiting, variation and combinationof any of the examples may occur. The examples cover all possibleproduction variants, as long as they do not depart from the scopedelimited by the appended claims which define the present invention.

Clauses:

Clause 1. A method for configuring a surgical guide and an associatedimplant for maxillofacial osteosynthesis, the method comprising:

-   -   accessing data indicative of a pre-operative maxillofacial        anatomy of a patient and generating a three-dimensional model of        said anatomy using said data;    -   simulating an osteotomy on the three-dimensional model of the        pre-operative maxillofacial anatomy, said simulated osteotomy        defining at least one cut that results in a second bone portion        that is separated from a first bone portion, said osteotomy        resulting in an absence of any bone coupling the first and        second bone portions together;    -   arranging the second bone portion in relation to the first bone        portion to generate a modified three-dimensional model        indicative of a desired post-operative orientation of the first        and second bone portions, said arrangement comprising at least        one or more of a translation of the second bone portion in        relation to the first bone portion and a rotation of the second        bone portion about an axis that is orientated at a non-zero        angle to a plane of the osteotomy;    -   defining, on the modified three-dimensional model, a first        plurality of attachment points for the implant on the first bone        portion and a second plurality of attachment points for the        implant on the second bone portion, wherein said first and        second plurality of attachment points are defined on the        modified three-dimensional model based on at least one location        of one or more anatomical features of the patient such that at        least a spacing distance between a first set of adjacent        attachment points is different from a spacing distance between a        second set of adjacent attachment points,    -   wherein the first and second sets of adjacent attachment points        comprise:    -   two sets of attachment points with each set comprising adjacent        attachment points on the same bone portion, or two sets of        attachment points with each set comprising a first attachment        point on the first bone portion and a second, adjacent        attachment point on the second bone portion;    -   determining a monolithic three-dimensional structure for the        implant that couples the first and second plurality of        attachment points in the modified three-dimensional model,        wherein the monolithic three-dimensional structure for the        implant has a shape that varies in each of three dimensions to        arrange the second bone portion relative to the first bone        portion in accordance with the desired post-operative        orientation, each of at least one of the attachment points        corresponding to an aperture for a bone fixation device in said        structure for the implant;    -   mapping the first and second plurality of attachment points to        corresponding locations on the three-dimensional model of the        pre-operative maxillofacial anatomy; and    -   determining a monolithic three-dimensional structure for the        surgical guide that couples the corresponding locations in the        three-dimensional model of the pre-operative maxillofacial        anatomy, wherein each of at least one of the corresponding        locations corresponds to a guide aperture in said structure for        the surgical guide.

Clause 2. A method for configuring a maxillofacial implant forosteosynthesis, the method comprising:

-   -   generating a three-dimensional model of a desired post-operative        maxillofacial anatomy of a patient, the three dimensional model        indicating at least a simulated osteotomy that defines at least        one cut that results in a second bone portion that is separated        from a first bone portion within the three-dimensional model,        said osteotomy resulting in an absence of any bone coupling the        first and second bone portions together, the desired        post-operative maxillofacial anatomy corresponding to a selected        arrangement of the second bone portion in relation to the first        bone portion, said arrangement comprising at least one or more        of a translation of the second bone portion in relation to the        first bone portion and a rotation of the second bone portion        about an axis that is orientated at a non-zero angle to a plane        of the osteotomy;    -   defining on the three-dimensional model a first plurality of        attachment points for the implant on the first bone portion and        a second plurality of attachment points for the implant on the        second bone portion,    -   wherein said first and second plurality of attachment points are        defined on the three-dimensional model based on at least one        location of one or more anatomical features of the patient such        that at least a spacing distance between a first set of adjacent        attachment points is different from a spacing distance between a        second set of adjacent attachment points,    -   wherein the first and second sets of adjacent attachments points        comprise:    -   two sets of attachment points with each set comprising adjacent        attachment points on the same bone portion, or    -   two sets of attachment points with each set comprising a first        attachment point on the first bone portion and a second,        adjacent attachment point on the second bone portion; and    -   determining a monolithic three-dimensional structure for the        implant that couples the first and second plurality of        attachment points in the three-dimensional model, wherein the        monolithic three-dimensional structure for the implant has a        shape that varies in each of three dimensions to arrange the        second bone portion relative to the first bone portion in        accordance with the desired post-operative orientation, each of        at least one of the attachment points corresponding to an        aperture said structure for a bone fixation device.

Clause 3. A method for configuring a maxillofacial surgical guide, themethod comprising:

-   -   accessing data indicating locations of a plurality of drill        holes defined in relation to a three-dimensional model of a        desired post-operative maxillofacial anatomy of a patient,    -   the three dimensional model indicating at least a simulated        osteotomy that defines at least one cut that results in a second        bone portion that is separated from a first bone portion within        the three-dimensional model, said osteotomy resulting in an        absence of any bone coupling the first and second bone portions        together,    -   the desired post-operative maxillofacial anatomy corresponding        to a selected arrangement of the second bone portion in relation        to the first bone portion, said arrangement comprising at least        one or more of a translation of the second bone portion in        relation to the first bone portion and a rotation of the second        bone portion about an axis that is orientated at a non-zero        angle to a plane of the osteotomy,    -   the plurality of drill holes comprising a first plurality of        drill holes on the first bone portion and a second plurality of        drill holes on the second bone portion, wherein said first and        second plurality of drill holes are defined based on at least        one location of one or more anatomical features of the patient        such that at least a spacing distance between a first set of        adjacent drill holes is different from a spacing distance        between a second set of drill holes, the first and second sets        of adjacent drill holes comprising two sets of drill holes with        each set comprising adjacent drill holes on the same bone        portion or two sets of drill holes with each set comprising a        first drill hole on the first bone portion and a second,        adjacent drill hole on the second bone portion;    -   accessing data indicative of a pre-operative maxillofacial        anatomy of the patient;    -   mapping, using a computer, the locations of the first and second        plurality of drill holes defined in relation to the        three-dimensional model of the desired post-operative        maxillofacial anatomy to corresponding locations in relation to        the pre-operative maxillofacial anatomy;    -   determining, using a computer, a monolithic three-dimensional        structure for the maxillofacial surgical guide that couples the        corresponding locations defined in relation to the pre-operative        maxillofacial anatomy, wherein a guide aperture for a given        drill hole is defined in said structure at a given corresponding        location.

Clause 4. A method according to any one of clauses 1 to 2 comprising:

-   -   manufacturing the implant based on the determined monolithic        three-dimensional structure for the implant.

Clause 5. A method according to clause 1 or clause 3 comprising:

-   -   manufacturing the surgical guide based on the determined        monolithic three-dimensional structure for the surgical guide.

Clause 6. A method according to clause 4 or clause 5, wherein saidmanufacturing comprises additive manufacturing based on data defining athree-dimensional structure.

Clause 7. A method according to clauses 1, 3 or 5,

-   -   wherein the three-dimensional structure for the surgical guide        defines an inner surface that varies in each of three        dimensions,    -   wherein the inner surface has a shape that aligns with an outer        surface defined by the first bone portion and the second bone        portion in a pre-operative state,    -   wherein the second three-dimensional structure is configured        such that the inner surface aligns with the outer surface at a        single position in three-dimensional space.

Clause 8. A method according to any one of clauses 1, 3, 5 or 7,comprising:

-   -   for at least one selected guide aperture in the monolithic        three-dimensional structure for the surgical guide, defining a        drill bush,    -   wherein said defining comprises determining a height for the        drill bush based on at least one location of one or more        anatomical features of the patient.

Clause 9. A method according to any one of clauses 1, 3, 5 or 7,comprising:

-   -   defining one or more osteotomy guides on the monolithic        three-dimensional structure for the surgical guide, each        osteotomy guide indicating a location for at least one cut.

Clause 10. A method according to any one of clauses 1, 3, 5 or 7,comprising:

-   -   defining one or more attachment points for attaching the        monolithic three-dimensional structure for the surgical guide to        one or more of the pre-operative first and second bone portions.

Clause 11. A method according to clause 10, wherein at least one of saidone or more attachment points for attaching the monolithicthree-dimensional structure for the surgical guide is co-incident with adefined osteotomy cut.

Clause 12. A method according to any one of the preceding clauses,comprising:

-   -   for a selected attachment point or drill hole, defining an angle        of orientation for an axis associated with a bore based on at        least one location of one or more anatomical features of the        patient.

Clause 13. A method according to clause 9, wherein the axis has an angleof orientation that is offset from a plane that is perpendicular to asurface of one of the first and second bone portions.

Clause 14. A method according to any one of the preceding clauses,wherein the second bone portion comprises a plurality of bone portionsthat result from a plurality of cuts.

Clause 15. A method according to any one of the preceding clauses,

-   -   wherein the method is repeated to determine a plurality of        monolithic three-dimensional structures for one or more of a        plurality of implants and a plurality of surgical guides,    -   wherein the method is repeated for a plurality of first bone        portions and a common second bone portion.

Clause 16. A method according to clause 15, comprising:

-   -   defining a portion of a first structure for a first implant or        first surgical guide that distinguishes said first structure        from a second structure for a second implant or second surgical        guide.

Clause 17. A method according to clause 15 or clause 16,

-   -   wherein one structure for a surgical guide corresponds to a        plurality of structures for an implant, or    -   a plurality of structures for a surgical guide corresponds to        one structure for an implant.

Clause 18. A maxillofacial implant for osteosynthesis comprising:

-   -   a first plurality of apertures for coupling the implant to a        first maxillofacial bone portion of a patient;    -   a second plurality of apertures for coupling the implant to a        second maxillofacial bone portion of a patient;    -   a monolithic three-dimensional structure that couples the first        and second plurality of apertures,    -   wherein the three-dimensional structure has a shape that varies        in each of three dimensions to arrange the second maxillofacial        bone portion relative to the first maxillofacial bone portion in        accordance with a desired post-operative orientation,    -   wherein the implant is arranged to arrange the second        maxillofacial bone portion relative to the first maxillofacial        bone portion following an osteotomy that defines at least one        cut that results in the second maxillofacial bone portion being        separated from the first maxillofacial bone portion, said        osteotomy resulting in an absence of any bone coupling the first        and second bone portions together,    -   wherein the desired post-operative orientation corresponding to        a selected arrangement of the second maxillofacial bone portion        in relation to the first maxillofacial bone portion, said        arrangement comprising at least one or more of a translation of        the second maxillofacial bone portion in relation to the first        maxillofacial bone portion and a rotation of the second        maxillofacial bone portion about an axis that is orientated at a        non-zero angle to a plane of the osteotomy,    -   wherein said first and second plurality of apertures are defined        on the implant based on at least one location of one or more        anatomical features of a patient such that at least a coupling        length of the structure between a first set of adjacent        apertures is different from a coupling length of the structure        between a second set of adjacent apertures,    -   wherein the first and second sets of adjacent apertures comprise        two sets of apertures with each set comprising adjacent        apertures on the same maxillofacial bone portion, or two sets of        apertures with each set comprising a first aperture on the first        maxillofacial bone portion and a second, adjacent aperture on        the second maxillofacial bone portion.

Clause 19. A maxillofacial surgical guide comprising:

-   -   a first plurality of apertures for guiding a drilling operation        with respect to a first maxillofacial bone portion of a patient;    -   a second plurality of apertures for guiding the drilling        operation with respect to a second maxillofacial bone portion of        a patient;    -   a monolithic three-dimensional structure that couples the first        and second plurality of apertures,    -   wherein the monolithic three-dimensional structure defines an        inner surface that varies in each of three dimensions,    -   wherein the inner surface has a shape that aligns with an outer        surface defined by the first maxillofacial bone portion and the        second maxillofacial bone portion in a pre-operative state,    -   wherein the monolithic three-dimensional structure is configured        such that the inner surface aligns with the outer surface in a        single configuration in three-dimensional space,    -   wherein said first and second plurality of apertures are defined        on the surgical guide based on at least one location of one or        more anatomical features of a patient such that at least a        coupling length of the structure between a first set of adjacent        apertures is different from a coupling length of the structure        between a second set of adjacent apertures,    -   wherein the first and second sets of adjacent apertures comprise        two sets of apertures with each set comprising adjacent        apertures on the same maxillofacial bone portion, or two sets of        apertures with each set comprising a first aperture on the first        maxillofacial bone portion and a second, adjacent aperture on        the second maxillofacial bone portion.

Clause 20. A maxillofacial surgical guide according to clause 19,comprising:

-   -   at least one drill bush associated with one of the first or        second plurality of apertures,    -   the at least one drill bush having a height determined in        relation to at least one location of one or more anatomical        features of the patient.

Clause 21. A maxillofacial surgical guide according to one of clauses 19and 20, wherein the monolithic three-dimensional structure for thesurgical guide comprises:

-   -   one or more osteotomy guides, each osteotomy guide indicating a        location for at least one cut.

Clause 22. A maxillofacial surgical guide according to any one ofclauses 19 to 21, comprising:

-   -   one or more apertures for attaching the monolithic        three-dimensional structure for the surgical guide to one or        more of the pre-operative first and second bone portions.

Clause 23. A maxillofacial surgical guide according to clause 22,wherein at least one of said one or more apertures for attaching themonolithic three-dimensional structure for the surgical guide isco-incident with a defined osteotomy cut.

Clause 24. A maxillofacial implant according to clause 18 or amaxillofacial surgical guide according to any one of clauses 19 to 23,wherein each aperture has a bore with a defined axis, the axis having anangle of orientation that is offset from a plane that is perpendicularto a surface of a respective monolithic structure at a location for theaperture.

Clause 25. A maxillofacial implant according to clause 18 or 24, or amaxillofacial surgical guide according to any one of clauses 19 to 24,wherein a portion of a first structure for said implant or said surgicalguide distinguishes said first structure from a second structure for asecond implant or second surgical guide.

Clause 26. A kit for maxillofacial osteosynthesis comprising:

-   -   a maxillofacial surgical guide according to clause 19;    -   a maxillofacial implant according to clause 20;    -   wherein locations of the first and second plurality of apertures        in the maxillofacial surgical guide correspond to mapped        locations of the first and second plurality of apertures in the        maxillofacial implant,    -   wherein the locations of the first and second plurality of        apertures in the maxillofacial surgical guide correspond to a        pre-operative maxillofacial anatomy, and    -   wherein the locations of the first and second plurality of        apertures in the maxillofacial implant correspond to a desired        post-operative maxillofacial anatomy.

What is claimed is:
 1. A method for configuring a maxillofacial implantfor osteosynthesis, the method comprising: generating, using a computer,a three-dimensional model of a desired post-operative maxillofacialanatomy of a patient, the three-dimensional model indicating at least asimulated osteotomy that defines at least one cut that results in asecond bone portion that is separated from a first bone portion withinthe three-dimensional model, the desired postoperative maxillofacialanatomy corresponding to a selected arrangement of the second boneportion in relation to the first bone portion, said arrangementcomprising at least one or more of a translation and a rotation of thesecond bone portion in relation to the first bone portion; defining,using a computer, on the three-dimensional model a first plurality ofattachment points for the implant on the first bone portion and a secondplurality of attachment points for the implant on the second boneportion, wherein said first and second plurality of attachment pointsare defined on the three-dimensional model based on at least one of athickness of a bone part and at least one location of one or moreanatomical features of the patient; and determining, using a computer,based on the first and second pluralities of attachment points, amonolithic three-dimensional structure for the implant that couples thefirst and second pluralities of attachment points in thethree-dimensional model, wherein the monolithic three-dimensionalstructure for the implant has a shape that varies in each of threedimensions to arrange the second bone portion relative to the first boneportion in accordance with the desired post-operative orientation, eachof at least one of the attachment points corresponding to an aperturefor a bone fixation device in said structure.
 2. Method according toclaim 1, wherein the osteotomy results in an absence of any bonecoupling the first and second bone portions together.
 3. Methodaccording to claim 1, wherein the first and second pluralities ofattachment points are defined such that at least a spacing distancebetween a first set of adjacent attachment points is different from aspacing distance between a second set of adjacent attachment points,wherein the first and second sets of adjacent attachments pointscomprise: two sets of attachment points with each set comprisingadjacent attachment points on the same bone portion, or two sets ofattachment points with each set comprising a first attachment point onthe first bone portion and a second, adjacent attachment point on thesecond bone portion.
 4. Method according to claim 1, wherein the one ormore anatomical features comprises at least one of a tooth root, a nerveand a blood vessel.
 5. Method according to claim 1, further comprising:for a selected attachment point, defining an angle of orientation for anaxis associated with a bore based on at least one location of one ormore anatomical features of the patient.
 6. Method according to claim 5,wherein the axis is offset from an axis perpendicular to a surface ofthe first or second bone portion.
 7. Method according to claim 1,wherein the second bone portion comprises a plurality of bone portionsthat result from a plurality of cuts.
 8. Method according to claim 1,wherein the method is repeated to determine a plurality of monolithicthree-dimensional structures for a plurality of implants, wherein themethod is repeated for a plurality of first bone portions and a commonsecond bone portion.
 9. Method according to claim 8, further comprising:defining a portion of a first structure for a first implant thatdistinguishes said first structure from a second structure for a secondimplant.
 10. Method according to claim 1, further comprising:manufacturing the implant based on the determined monolithicthree-dimensional structure.
 11. Method according to claim 10, whereinsaid manufacturing comprises additive manufacturing based on datadefining a three-dimensional structure.
 12. A maxillofacial implant forosteosynthesis comprising: a first plurality of apertures for couplingthe implant to a first maxillofacial bone portion of a patient; a secondplurality of apertures for coupling the implant to a secondmaxillofacial bone portion of the patient; a monolithicthree-dimensional structure that couples the first and second pluralityof apertures, wherein the three-dimensional structure has a shape thatvaries in each of three dimensions to arrange the second maxillofacialbone portion relative to the first maxillofacial bone portion inaccordance with a desired post-operative orientation, wherein theimplant is arranged to arrange the second maxillofacial bone portionrelative to the first maxillofacial bone portion following an osteotomythat defines at least one cut that results in the second maxillofacialbone portion being separated from the first maxillofacial bone portion,wherein the desired post-operative orientation corresponds to a selectedarrangement of the second maxillofacial bone portion in relation to thefirst maxillofacial bone portion, said arrangement comprising at leastone or more of a translation and a rotation of the second maxillofacialbone portion in relation to the first maxillofacial bone portion,wherein said first and second pluralities of apertures are defined onthe implant based on at least one of a thickness of a bone part and atleast one location of one or more anatomical features of a patient suchthat at least a coupling length of the structure between a first set ofadjacent apertures is different from a coupling length of the structurebetween a second set of adjacent apertures, wherein the first and secondsets of adjacent apertures comprise two sets of apertures with each setcomprising adjacent apertures on the same maxillofacial bone portion, ortwo sets of apertures with each set comprising a first aperture on thefirst maxillofacial bone portion and a second, adjacent aperture on thesecond maxillofacial bone portion.
 13. Maxillofacial implant accordingto claim 12, wherein at least one aperture has a bore with a definedaxis, the axis having an angle of orientation that is offset from anaxis that is perpendicular to a surface of the monolithic structure at alocation for the aperture.